Aluminium oxide is impermeable and, unlike the oxide layers on many other metals, it adheres strongly to the parent metal. If damaged mechanically, aluminiumâs oxide layer repairs itself immediately.
Saliva helps remove oral waste and cavity-causing bacteria, protects teeth from decay by neutralizing harmful acids, and helps re-mineralize tooth enamel. Saliva also keeps oral tissues healthy by preventing infection by controlling bacteria and fungi in the mouth.
There are two major types of saliva that are secreted from the salivary glands and they are serous and mucinous. The submandibular gland is the only mixed salivary gland that secretes both types in a 3:2 ratio of serous to mucous respectively. The parotid gland is the only gland that secretes purely serous saliva, while the sublingual gland and minor salivary glands secrete purely mucinous saliva. The total daily output of saliva in an adult is between one and one and a half liters of saliva.